It concerns a continuous joint for a seat with an adjustable back which is principally used to adjust the back of a vehicle seat but can also be used for other types of seats.
This continuous joint comprises a fixed plate, integral with the seat-part of the seat and a movable plate, integral with the back, said plates being laterally secured to each other in confronting relationship. One of said plates is provided with a shaft disposed about a central axis. An eccentric constituting a cam is provided with a bearing aperture in which is seated the shaft. This eccentric is rotatable about the central axis enabling the angular position of one of the two plates to be varied in relation to the other by partial engagement of at least two sets of teeth. A first set of teeth, integral with one of the two plates, is centered on said central axis about which the eccentric constituting a cam turns and a second corresponding set of teeth is integral with a part driven by the eccentric constituting a cam in such a way as to displace around said central axis the partial engagement zone. According to the invention the eccentric constituting a cam has on its periphery, in the most eccentric zone in relation to the axis, an elastic bearing made of a metal or a metal alloy integral with this eccentric constituting a cam. This elastic bearing is elastically held directly or indirectly against the face of the tooth part driven by this eccentric constituting a cam in such a way as to hold the second set of teeth integral with this part against the first set of teeth in the partial engagement zone.
The bearing aperture of the eccentric constituting a cam is provided with two main support zones in relief on which the shaft bears to provide a reactive force to the force applied by said elastic bearing against the driven face of said tooth part. Said support zones are angularly spaced 90.degree.-150.degree. apart and preferably about 120.degree. apart, on opposed sides of a plane containing the central axis and a diametral line symmetrically bisecting the partial engagement zone of said at least two sets of teeth.